The present invention relates generally to devices for molding container closures, particularly by injection molding, and specifically to an apparatus for molding closures having tamper evident or so-called breakaway bands.
Tamper evident closures employing breakaway bands are commonly used on relatively small-necked containers such as plastic milk bottles and motor oil bottles. There has been a demand, particularly among food processors and packagers, as well as manufacturers of agricultural pesticides, for visually distinctive tamper evident container closures for bottles having relatively larger neck diameters on the order of 2.5-3.0 inches (63 mm). Packagers in these industries are particularly vulnerable to counterfeit packages or look-alike packages containing inferior counterfeit products. Visually distinctive closures are considered to be harder to reproduce by counterfeiters, and as such are thought to deter counterfeiting.
Furthermore, there has been a demand among food processors for a replacement for the traditional metal cap and peal-off foil or plastic seals commonly found on large-mouthed containers of mayonnaise, salad dressing and similar foodstuffs. Such containers are expensive to package in that the seal material is costly, as is the two-step assembly operation (closure and seal are separately applied).
In addition, relatively wide-mouthed containers are also susceptible to backing off or gradual unthreading of conventional closures from the container neck or finish during packaging and shipping. Commonly-assigned U.S. Pat. No. 4,913,299 discloses a closure and container having an anti-backoff system of peripherally projecting teeth on the container neck and a corresponding plurality of spaced recesses on the lower edge of the closure skirt which engage the teeth and thus prevent unwanted unthreading of the closure. Although satisfactory in preventing backing off of the closure, due to shortcomings of conventional molding machinery, the closure of the above-identified patent has not been provided with a tamper evident feature such as a breakaway band.
There has been a demand in the food and pesticide industries, among others, for providing such a closure with a breakaway band to obtain the desired anti-counterfeiting properties. However, closure manufacturers have been unable to supply such a closure due to the significant difficulty in efficiently molding the many undercuts inherent with a combination of the anti-backoff recesses and a breakaway band. Such operations were unavailable through conventional injection molding presses, regardless of whether they were of the commonly known stripper type or the unscrewing type.
In commonly-assigned U.S. patent application Ser. No. 973,029, filed Nov. 6, 1992, which is incorporated herein by reference, there is disclosed a tamper evident closure having both a breakaway band and an anti-backoff feature. In order to more efficiently mass produce the closure of that invention, the above-identified difficulties in molding technology needed to be overcome.
A specific difficulty encountered in the molding of closures having both anti-backoff features and a breakaway band is that, due to the several undercut formations on the closure, mold slides are required. Upon the completion of each molding cycle, it has been found that finished closures often adhere to the mold slides, requiring some sort of supplemental removal operation. Removal of the stuck closures must be accomplished by hand, which slows production.
Thus, a major object of the present invention is to provide a molding apparatus for a tamper evident closure constructed so that the finished closures do not remain attached to the mold slide.
A further object of the present invention is to provide a molding apparatus for a closure having a breakaway band as well as an anti-backoff feature.
Another object of the present invention is to provide a molding apparatus for tamper evident closures which is readily convertible from molding closures with an anti-backoff feature to closures not having such feature.